The deviation-correction system is widely used in automated assembly and moving object positioning systems. For example, using a deviation-correction control system can ensure material meets the requirements of process or product quality during the procedures of channeling, reeling, transmission, splitting, concatenation and jointing. In addition, a deviation-correction system can be used to achieve the accurate vehicle positioning, etc. At present, the deviation-correction system is classified primarily into three types as follows:
1) A sensor deviation-correction control system is a system in which sensors detect the edge or line of roll goods, read deviation between an actual position and a preset position of the roll goods, convert the deviation into an electrical signal in proportional to it, and then input the signal to a controller, in which the signal is amplified and calibrated before it is transmitted to an actuator. Based on the magnitude of the signal, the actuator drives a guide bracket to replace the roll goods in the preset position. Various sensors, such as photoelectric sensor, ultrasonic sensor and line-type tracking sensor, are employed to meet the need for deviation correction from various roll goods, such as fully transparent roll goods, photosensitive film, steel plate roll goods and roll goods imprinted with contrast line for tracking. In this case, the deviation-correction accuracy can fall into a range of 0.5 mm or less.
2.) A laser deviation-correction control system is a system in which a laser beam is emitted along the designed axis of the conduit by a laser transmitter, and then is received by a laser receiver within a tool head. After the comparison between the laser beam and the actual center position of the tool head, the error signal is fed back to a computer for further processing. Then, a control apparatus adjusts the tool head based on the displacement error, thereby implementing the deviation-correction function.
3) A GPS based deviation-correction system is a GPS system employed by Shanghai Zhenhua Port Machinery Co. Ltd (ZPMC) for container crane and crossbeam-lifting Twin 40 ft quayside container crane so as to realize a error-correction positioning system with an error less than 15 mm.
In the above systems, the first one has a high accuracy, but a narrow applicability. The second and third ones are applicable to positioning of moving objects, while their cost is high.